Known methods for achieving a compact data system storage of an entity key set include front-end and rear-end compression techniques, explained by C. J. Date in the third edition of `An Introduction to Database Systems`, Addison-Wesley pages 51-52, and by James Martin in the second edition of `Computer Data-Base Organization`, Prentice-Hall, pages 517-526. A well known word processing program named `Word Plus` is using a similar method to compress a set of textural words, for use as a correct-spelling reference. A developed version of this program requires 158,000 bytes of storage to hold 54,000 different Swedish words.
The efficiency of data compression arrangements constructed and operating according to this invention may be enhanced by using conventional Huffman coding techniques. In 1952 David A. Huffman's paper `A Method for the construction of Minimum-Redundancy Codes` was published in Proc. IRE, 40(9). More recently the Huffman coding technique was explained by Gilbert Held in a Wiley Heyden Publication `Data Compression`, copyright 1983 and reprinted 1984.